Southwestern archaeologists have traditionally devoted much attention to inventory and description of material culture change between the Pithouse and Pueblo periods. Unfortunately, our understanding of the ecological, demographic, and organizational aspects of the Pithouse-to-Pueblo transition is much less advanced. The present study attempts to remedy this deficiency for at least one portion of the Southwest, relying largely on survey data from the Mogollon culture area of extreme western Texas. Three major aspects of Pithouse-to-Pueblo change are considered. These are demographic change, subsistence pattern change, and social-organizational change. Basically, the transition is seen as a fundamental adaptive reorientation in which a small-scale, extensive, generalized adaption is replaced by one which was larger in scale, more intensive, and more specialized in focus than ever before. Factors motivating this transition are considered, and the supra-local applicability of the resulting model is discussed.